Core B is the Genetically Modified Mouse Resources Core. All three projects will make extensive use of genetically modified mice for their proposed experiments. Centralized localization of the animals, rational control and sharing of the breeding stocks, and centralization of genotype analyses will maximize efficiency and minimize costs associated with the production of the mice needed for the propose experiments. Specific activities of Core B include (1) Assistance in the generation of additional genetically modified mouse models, (2) Establishment and maintenance of breeding stocks, (3) Generation and genotype analysis of transgenic and/or knock-out mice, (4) Generation and collection of timed pregnancies, (5) Fostering, weaning and storage of the experimental animals, (6) Distribution of genetically modified mouse models, and (7) Delivery of experimental animals to the appropriate laboratory for use. Core personnel are already well-trained in all aspects of the services to be provided. Given the heavy reliance on genetically modified animals, the importance of Core B to the success of the Program Project Grant application cannot be overstated.